Rosette-forming Glioneuronal Tumor Research Articles

Thalamic rosette-forming a glioneuronal tumor in an elderly patient: Case report and literature review

The rosette-forming glioneuronal tumor (RGNT) is a novel type of brain tumor recently listed in the WHO 2007 classification of central nervous system (CNS) tumors. We report the case of a 75-year-old woman harboring a thalamic RGNT with third ventricle dissemination. Age and location make the present case exceptional and which has never previously been reported. A review of the clinical, pathological and radiological features is presented along with the relevant literature.

RARE-22MIXED GLIONEURONAL TUMORS WITH DNET AND RGNT FEATURES: CASE REPORT AND LITERATURE REVIEW

OBJECTIVE: Case report and literature review of mixed glioneuronal tumors with rosette-forming glioneuronal tumor (RGNT) and dysplastic neuroepithelial tumor (DNET) histology. METHODS/RESULTS: A 35 y/o male presented with a third ventricular mass. The mass was sub-totally resected with residual tumor in the thalamus. Pathologic features of a RGNT and DNET were present. The tumor was BRAF V600E wild-type and a PIK3CA mutation (E545K, c.1633G > A) was found. Searching the English literature we found 4 other cases of mixed glioneuronal tumors with RGNT/DNET features; PIK3CA mutations were not assessed in these cases. There are 6 cases of pure RGNTs in the literature with PIK3CA mutations. CONCLUSIONS: A rare sub-set of glioneuronal tumors have mixed RGNT/DNET features. PIK3CA mutations are present in some pure RGNTs, and our case suggests this mutation may be present in cases with mixed DNET/RGNT histology. This finding may have implications for defining tumor biology and pursuing targeted therapy in select cases.

Rosette-forming glioneuronal tumor of the fourth ventricle

Objective To explore the clinicopathological features of rosette-forming glioneuronal tumor (RGNT) of the fourth ventricle. Methods The clinical manifestations, neuroimaging, histopathological and immunohistochemical features were analysed in one case of RGNT of the fourth ventricle, and related literatures were reviewed. Results A 24-year-old female presented with progressive dizziness under no obvious predisposing causes and dyskinesia such as stumbling. MRI revealed expansion of the fourth ventricle, and a mass with long T 1 WI and T 2 WI signal and clear boundary could be seen within the fourth ventricle. The border of tumor showed slight enhancement. At surgery, it was observed that the solitary tumor arised from the fourth ventricle and appeared well demarcated with rhomboid fossa. The tumor was blocking the aqueduct of sylvius before it was removed. Microscopically, the tumor exhibited both neuronic and astrocytic components. In the neuronic components, neurocytes formed neurocytic rosettes and perivascular pseudorosettes. At the center of the neurocytic rosettes, there was an eosinophilic core and some region consisted of microcysts. While the astrocytic components of the tumor revealed typical pilocytic astrocytoma structure. The center of neuronic rosettes and perivascular pseudorosettes displayed strong positive staining with synaptophysin (Syn) and oligodendrocytes transcription factor-2 (Olig-2). The astrocytic components showed positive immunostaining of glial fibrillary acidic protein (GFAP). There were focal and partial positive immunostaining of neuron-specific enolase (NSE) in both components of the tumor. The Ki-67 labeling index was 1.50%-2.00% in two components. Conclusions Rosette-forming glioneuronal tumor of the fourth ventricle is an unusual neuronal and mixed neuronal-glial tumors. The imaging examination showed solid or mixed solid-cystic mass at the fourth ventricle with well demarcated border. The lesion has two characteristic components and the distinctive immunostaining of GFAP and Syn expression will help the differential diagnosis. DOI: 10.3969/j.issn.1672-6731.2015.11.013

Rosette-forming glioneuronal tumor outside the fourth ventricle: a case-based update.

Rosette-forming glioneuronal tumors (RGNTs) that do not involve the fourth ventricle are rare. RGNTs were originally thought to be exclusively localized into the fourth ventricle but were found in various anatomical localizations. We review the literature and found 32 cases of this particular RGNT. The outcome was excellent with no mortality reported after surgical treatment. Only two patients had received adjuvant therapy for progression. We added one case of a RGNT located in the cerebellar hemisphere. She underwent a subtotal removal with no evidence of progression after. This WHO grade I tumor with a specific biphasic histopathology is of a good oncological outcome after surgical treatment. A long follow-up is needed as recurrence or metastatic progressions exist.

Uncommon pediatric tumors of the posterior fossa: pathologic and molecular features.

Three tumors are commonly encountered in the posterior fossa of children: pilocytic astrocytoma (PA), medulloblastoma (MB), and ependymoma. However, a variety of additional tumors may occasionally be appreciated. Appropriate and successful treatment of these less common cases is predicated upon correct pathologic diagnosis. Reviewed herein are five less common tumors that may affect the posterior fossa of children: (1) "embryonal tumor with multilayered rosettes" (ETMR); (2) "cribriform neuroepithelial tumor" (CRINET); (3) "rosette-forming glioneuronal tumor" (RGNT); (4) "diffuse pilocytic astrocytoma" (dPA); and, (5) "desmoplastic small round cell tumor" (DSRCT). Each of the foregoing has a varying predilection for children and a posterior fossa location. For example, RGNT by definition arises in association with the 4th ventricle; while the mean age of those afflicted is 33, children may also be affected. Likewise, descriptions of dPA are generally restricted to the posterior fossa, and in particular, the cerebellum of children. Alternatively, DSRCT is a form of undifferentiated sarcoma that characteristically originates in the abdomen of children, but on occasion arises from the tentorium of young adults and children. The relevant molecular genetic underpinnings for each of the tumors highlighted herein have been well described and may carry diagnostic utility, not to mention clues as to underlying etiology. A number of pediatric brain tumors have a tendency to occur in the posterior fossa. While far less common than PA, MB, or ependymoma, the entities highlighted herein appear to have a degree of proclivity for the posterior fossa of children and as such warrant due consideration in the clinicopathologic workup of these cases.

SLC44A1–PRKCA fusion in papillary and rosette-forming glioneuronal tumors

We investigated the fused protein of solute carrier family 44 choline transporter member 1 (SLC44A1) and protein kinase C alpha (PRKCA) in three patients with papillary glioneuronal tumors (PGNT). PGNT and rosette-forming glioneuronal tumors (RGNT) are recently identified, unusual glioneuronal tumor variants which were categorized as novel tumor entities in the 2007 World Health Organization classification system. The molecular background of these tumors remains poorly understood due to the paucity of studies. The SLC44A1–PRKCA fusion was recently detected in three cases of PGNT. We invesitgated for the SLC44A1–PRKCA fusion protein in the three PGNT patients and a further two with RGNT using fluorescence in situ hybridization. Two out of the three PGNT patients had a fused signal (paired red–green signal) representing a rearrangement on chromosomes 9 and 17. A normal signal pattern was observed in the third PGNT patient. Neither of the two RGNT patients demonstrated a fused signal. This suggests that the SLC44A1–PRKCA fusion is a characteristic alteration in PGNT but not RGNT. Therefore, it is a potential biomarker of PGNT. The paired red–green signal that was observed in the PGNT patients implies the presence of a different breakpoint than that previously reported in the 9q31 and 17q24 genes.

Analysis of a Novel Translocation, T(9;17)(Q31;Q24), in Rosette-Forming Glioneuronal Tumors

ABSTRACT Aim: Papillary glioneuronal tumor (PGNT) and rosette-forming glioneuronal tumor (RGNT) were recently established unusual glioneuronal phenotypes and were categorized as a novel tumor entity in the 2007 World Health Organization classification. The molecular background of these glioneuronal tumors remains poorly understood due to a paucity of reports. Recently, the SLC44A1-PRKCA fusion has been identified in 3 cases of PGNT. Methods: The aim of this study was to confirm it in our 3 cases of PGNT and analyze the presence of specific fusion in 2 cases of RGNT, using fluorescence in situ hybridization. Results: Two out of three PGNT cases showed one adjacent red-green signal pair representing the rearrangement on chromosome 9 and 17, but not a complete fused yellow signal. Normal signal pattern was observed in the other PGNT case. Neither of two RGNT cases revealed adjacent red-green signal pair or yellow signal. Conclusions: The SLC44A1-PRKCA fusion is a characteristic alteration in PGNT but not in RGNT, and is suggested as a potential biomarker of PGNT. One adjacent red-green signal pair observed in the PGNTs may imply the presence of different breakpoints from those previously reported in the 9q31 and 17q24 genes. Disclosure: All authors have declared no conflicts of interest.

An individual patient data meta-analysis on characteristics and outcome of patients with papillary glioneuronal tumor, rosette glioneuronal tumor with neuropil-like islands and rosette forming glioneuronal tumor of the fourth ventricle.

Background and PurposeIn 2007, the WHO classification of brain tumors was extended by three new entities of glioneuronal tumors: papillary glioneuronal tumor (PGNT), rosette-forming glioneuronal tumor of the fourth ventricle (RGNT) and glioneuronal tumor with neuropil-like islands (GNTNI). Focusing on clinical characteristics and outcome, the authors performed a comprehensive individual patient data (IPD) meta-analysis of the cases reported in literature until December 2012.MethodsPubMed, Embase and Web of Science were searched for peer-reviewed articles reporting on PGNT, RGNT, and GNTNI using predefined keywords.Results95 publications reported on 182 patients (PGNT, 71; GNTNI, 26; RGNT, 85). Median age at diagnosis was 23 years (range 4–75) for PGNT, 27 years (range 6–79) for RGNT, and 40 years (range 2–65) for GNTNI. Ninety-seven percent of PGNT and 69% of GNTNI were located in the supratentorial region, 23% of GNTNI were in the spinal cord, and 80% of RGNT were localized in the posterior fossa. Complete resection was reported in 52 PGNT (73%), 36 RGNT (42%), and 7 GNTNI (27%) patients. Eight PGNT, 3 RGNT, and 12 GNTNI patients were treated with chemo- and/or radiotherapy as the primary postoperative treatment. Follow-up data were available for 132 cases. After a median follow-up time of 1.5 years (range 0.2–25) across all patients, 1.5-year progression-free survival rates were 52±12% for GNTNI, 86±5% for PGNT, and 100% for RGNT. The 1.5-year overall-survival were 95±5%, 98±2%, and 100%, respectively.ConclusionsThe clinical understanding of the three new entities of glioneuronal tumors, PGNT, RGNT and GNTNI, is currently emerging. The present meta-analysis will hopefully contribute to a delineation of their diagnostic, therapeutic, and prognostic profiles. However, the available data do not provide a solid basis to define the optimum treatment approach. Hence, a central register should be established.

FGFR1 mutations in Rosette-forming glioneuronal tumors of the fourth ventricle.

Rosette-forming glioneuronal tumors (RGNTs) are rare glioneuronal tumors of the fourth ventricle region that preferentially affect young adults. Despite their histologic similarity with pilocytic astrocytomas (PAs), RGNTs do not harbor KIAA1549-BRAF fusions or BRAF mutations, which represent the most common genetic alteration in PAs. Recently, mutations affecting the hotspot codons Asn546 and Lys656 of fibroblast growth factor receptor 1 (FGFR1) have been described in PAs. They are considered to be the most frequent mechanism of mitogen-activated protein kinase activation, alternative to KIAA1549-BRAF fusion and BRAF mutations. To uncover possible molecular similarities between RGNTs and PAs, we performed a mutational study of FGFR1 in 8 RGNTs. An FGFR1 N546K mutation and an FGFR1 K656E mutation were found in the tumors of 2 patients. Notably, the patient with an FGFR1 K656E mutated RGNT had undergone a resection of a diencephalic pilocytic astrocytoma with pilomyxoid features 5 years before the discovery of the fourth ventricle tumor; the mutational analysis uncovered the presence of the same FGFR1 K656E mutation in the diencephalic tumor. These results indicate that, in addition to histologic similarities, at least a subgroup of RGNTs may show close molecular relationships with PAs. Whether FGFR1 mutated RGNTs represent a specific subset of this rare tumor entity remains to be determined.

Rosette-Forming Glioneuronal Tumor That Did Not Recur for Six Years: A Rare Case Report

Rosette-forming glioneuronal tumor (RGNT) is a central nervous system tumor type that is rarely seen and classified as grade 1 tumor by World Health Organization. They can be seen in several different locations of the brain, in the fourth ventricle. We have reviewed the English-written literature; there are 72 cases about RGNT of the fourth ventricle and most of them are of young women. On the contrary, in our case report, we analyzed a case of a 33-year-old male patient who had a long-lasting headache complaint and was diagnosed afterwards with RGNT and had no recurrence in his 6-year follow-up. J Med Cases. 2014;5(5):304-307 doi: http://dx.doi.org/10.14740/jmc1772w

Clinicopathological analysis of unusual rosette-forming glioneuronal tumor in brain parenchyma

Background Rosette-forming glioneuronal tumor (RGNT) is a rare and novel brain tumor. It affects mainly young adults and arises in the midline, primarily involving the cerebellum, and the walls or floor of the fourth ventricle. The tumor is composed of distinctive histological components, uniform neurocytes forming rosettes and (or) perivascular pseudorosettes, as well as astrocytic component resembling pilocytic astrocytoma. To our best knowledge, no more than 50 cases of RGNT have been described in the literatures to date and found commonly in association with the ventricular system. Only a few cases have been known to occur at sites outside of its usual location. Herein, we present a rare case of RGNT of brain parenchyma. Due to its rarity and non-specific appearance in radiological examination, it is a diagnostic challenge for radiologists and histopathologists to differentiate RGNT in unusual sites from other intracranial lesions because of its similarities in radiological and histological findings. The aim of this study is to summarize the clinicopathological features of RGNT and discuss the differential diagnosis of histologically similar tumors in brain. Methods The clinical manifestation of a patient with RGNT occurring in left frontal lobe was presented retrospectively. Resected mass was routinely paraffin-embedded and stained with Hematoxylin and Eosin. Dako EnVision immunohistochemical staining system was used to detect the tumor antigen expressions, including glial fibrillary acidic protein (GFAP), S-100 protein (S-100), cytokeratin (CK), neuronal nuclear antigen (NeuN), synaptophysin (Syn), neuron-specific enolase (NSE), chromogranin A (CgA), oligodendrocytes transcription factor-2 (Olig-2), epithelial membrane antigen (EMA) and Ki-67 (MIB-1). Results A 12-year-old girl presented with 2-year history of twitches and mild headache. MRI revealed a solid well-circumscribed lesion in left frontal lobe with mild heterogeneous enhancement. The lesion was observed to locate in brain parenchyma and there was no evidence of tumor infiltrating in ventricular system. Craniotomy was performed and the tumor was removed totally. Histological examination revealed that the tumor was distinctive in its juxtaposition of patterned neurocytic and pilocytic astroglial components. The neurocytic component showed the tumor cells had small, uniform round nuclei with scant cytoplasm and formed narrow perivascular pseudorosettes or Homer-Wright-like rosettes arrays of neurocytic nuclei around delicate eosinophilic neuropil cores. The glial component tended to exhibit pilocytic astrocytoma-like morphology with long, hair-like processes and Rosenthal fibers. Immunohistochemical staining showed that the tumor cells in glial component were diffusely positive for GFAP and S-100, but negative for NeuN, Syn and NSE. However, perivascular pseudorosettes or Homer-Wright-like rosettes were positive for Syn and Olig-2, and negative for GFAP. Ki-67 index was low and less than 1%. Based on clinical presentation and histological findings, a final histological diagnosis of RGNT in brain parenchyma, WHO grade Ⅰ, was made according to the criteria of WHO classification. The patient has not received chemotherapy and attended follow-up for 12 months, without any neurological deficit or signs of recurrence. Conclusions RGNT is a rare tumor and classified as mixed neuronal-glial tumor. RGNT probably derives from a common progenitor cell originated from subependymal plate or brain parenchyma, able to differentiate toward both glial and neuronal phenotype. RGNT in brain parenchyma is also observed to have the similar biological behaviors and histopathological characteristics with its intra-ventricular counterpart. With similarities in histological findings, it may be difficult to differentiate RGNT from extraventricular neurocytoma, dysembry oplastic neuroepithelial tumor (DNT), and ependymoma with neuronal differentiation or neuropil-like islands. The presence of distinct low-grade glial component in the tumor and appropriate immunohistochemical profile are necessary for correct diagnosis. doi: 10.3969/j.issn.1672-6731.2014.03.014

Rosette forming glioneuronal tumor of the fourth ventricle in squash cytology smear

Rosette forming glioneuronal tumor (RGNT) is a recently recognized and extremely rare glioneuronal tumor occurring in the fourth ventricle. It is crucial for the cytopathologist to be aware of this entity as it can be easily mistaken for more common neoplasms occurring at this site. We present here the cytology of such a rare case of RGNT that was misdiagnosed as ependymoma. The varying cytological features of this entity, as well as the common diagnostic difficulties encountered in cytology, are highlighted in this report.

Rosette-forming Glioneuronal Tumors in the Posterior Third Ventricle

Rosette-forming glioneuronal tumor (RGNT) is a rare brain tumor found almost exclusively within the fourth ventricle. These grade I tumors were first included in the World Health Organization (WHO) Classification for the central nervous system in 20071. Since then, approximately 49 cases have been published.There are no reported cases of RGNT within the third ventricle, although this tumor has also been described in the pineal region, the tectum and within the aqueduct. Supratentorial localization is quite rare, with only three published: one was found in the septum pellucidum, another within the optic nerve in neurofibromatosis type 1 (NF1) patient and one in a patient with multiple RGNT in the lateral ventricle. The authors report the first case series in the literature of RGNT occurring within the posterior third ventricle.

Rosette-forming glioneuronal tumor of the cerebellum in statu nascendi: an incidentally detected diminutive example indicates derivation from the internal granule cell layer

Rosette-forming glioneuronal tumor (RGNT) is a recently introduced, indolent neoplasm composed of diminutive circular aggregates of neurocytic-like cells on a noninfiltrative astrocytic background, typically located in the cerebellar midline The traded concept of RGNT being derived from site-specific periventricular precursors may be questioned in the face of extracerebellar examples as well as ones occurring in combination with other representatives of the glioneuronal family. We describe a hitherto not documented example of asymptomatic RGNT discovered during autopsy of a 74-year-old male. Located in the tuberal vermis, this lesion of 6 mm diameter consisted of several microscopic nests of what were felt to represent nascent stages of RGNT, all of them centered on the internal granular layer, and ranging from mucoid dehiscences thereof to fully evolved - if small - tumor foci. Molecular genetic analysis revealed a missense mutation in Exon 20 of the PIK3CA gene involving an A→G transition at Nucleotide 3140. On the other hand, neither codeletion of chromosomes 1p/19q nor pathogenic mutations of IDH1/2 were detected. By analogy with in situ paradigms in other organs, we propose that this tumor is likely to have arisen from the internal granular layer, rather than the plate of the 4th ventricle. A suggestive departure from the wholesale argument of "undifferentiated precursors", this finding also indirectly indicates that a subset of non-classical RGNTs - in particular extracerebellar examples, whose origin cannot be mechanistically accounted for by either of the above structures - may possibly reflect an instance of phenotypic convergence, rather than a lineage-restricted entity.

Rosette-forming glioneuronal tumor of the fourth ventricle with neurocytoma component

Rosette-forming glioneuronal tumor (RGNT) was first published in 2002 and was described as a benign and indolent tumor. It was also included in the 2007 World Health Organization (WHO) classification of tumors as a grade 1 tumor for its benign clinical behavior and the possibility of surgical cure. Pathologically, RGNT is a mixed neuronal-glial tumor which consists of two distinct histological components-one with uniform neurocytes forming rosettes and/or perivascular pseudorosettes and the other being astrocytic in nature resembling pilocytic astrocytoma (biphasic pattern). We present the clinical course and pathological findings of two distinctively different cases. The first one was a 4-year-old girl with head trauma and a tumor which was incidentally found by CT. Pathology revealed that the tumor contained neurocytoma components and areas of relatively high proliferative ability with the first report of the presence of midsized bright elliptic cells. The other case was a 19-year-old girl whose imaging studies showed hydrocephalus and a brain stem tumor. She underwent endoscopic third ventriculostomy and biopsy, followed by observation. An MRI taken 6 months later showed progression of the tumor and she subsequently had the tumor excised. We are considering the possibility for our RGNT cases to correspond to a higher WHO grade as they have shown rapid progression, contrary to the already established, and their character, origin, differential diagnosis, and treatment plans have been discussed.

Tumor glioneuronal formador de rosetas del cuarto ventrículo. Presentación de un caso y revisión de la literatura

Rosette-forming glioneuronal tumor (RGNT) of the fourth ventricle is a rare tumor that has been recently characterized. RGNT was included as a new glioneuronal tumor in 2007 by the World Health Organization (WHO) in classification of tumors of the central nervous system. Within this group we found 34 documented cases. We present a new case of RGNT of the fourth ventricle with intratumoral posttraumatic bleeding and review the existing literature of this new entity.A 30-year-old patient was admitted after suffering mild traumatic brain injury (TBI) had headache, diplopia and ataxia. Studies of computed tomography and magnetic resonance imaging revealed a tumor at the fourth ventricle with intralesional bleeding and areas of calcification. She was operated performing macroscopically complete tumor resection. Pathologic examination showed a rosette-forming glioneuronal tumor of the fourth ventricle.The RGNT of the fourth ventricle are rare and affect young adults. The evidence shows that the prognosis is usually favorable but there is the possibility of progression and recurrence. Intratumoral hemorrhage is a very unusual presentation that involves risk to the patient's life. Surgical resection should be careful due to the location of these lesions and their extension into critical areas, all patients regardless of extent of resection achieved require a long-term monitoring of the risk of late relapse.

Coexpression of glial and neuronal markers in the neurocytic rosettes of rosette-forming glioneuronal tumors

Rosette-forming glioneuronal tumor of the fourth ventricle (RGNT) is a new entity in the WHO 2007 Classification of Tumors of the Central Nervous System. RGNT has two components: neurocytic rosettes and low-grade gliomas. Neurocytic rosettes are conventionally described as consisting of uniform neurocytes. However, some studies have reported rosette-forming tumor cells that expressed glial markers such as Olig2. We indicated the expression of glial markers including Olig2, cyclinD1, glial fibrillary acidic protein (GFAP), and platelet-derived growth factor receptor alpha (PDGFRα) in the neurocytic rosettes in our previous study, and we suggested that these tumor cells had a heterogeneous nature. In this study, we used double and triple immunostaining to demonstrate that these tumor cells have both glial and neuronal characteristics. We found that rosette-forming tumor cells coexpressed Olig2/cyclinD1 and synaptophysin. Furthermore, the cores of the rosettes coexpressed GFAP/PDGFRα in the peripheral zone and synaptophysin in the central zone. These findings imply that rosette-forming tumor cells have a similar nature to neuronal-glial progenitor cells, and we believe that the nomination "neurocytic rosette" may be unsuitable given their heterogeneous nature. Our study appears to clarify some of the properties of RGNT tumor cells and may help elucidate the histogenesis of RGNT.

From the Radiologic Pathology Archives: Intraventricular Neoplasms: Radiologic-Pathologic Correlation

A variety of neoplasms may arise in the ventricular system. Intraventricular neoplasms may be discovered as an incidental finding at cross-sectional imaging or may manifest with varied symptoms depending on their location, including symptoms of increased intracranial pressure. These lesions may arise from various ventricular structures, including the ependymal lining (eg, ependymoma), subependymal layer (eg, subependymoma), or choroid plexus (eg, choroid plexus neoplasms), or they may have a cell of origin that has yet to be determined (eg, chordoid glioma). Other neoplasms involving the ventricular system include central neurocytoma, subependymal giant cell tumor, meningioma, rosette-forming glioneuronal tumor, and metastases. The differential diagnosis for intraventricular neoplasms can be broad, and many of them have similar patterns of signal intensity and contrast enhancement at imaging. However, the location of the lesion in the ventricular system-along with knowledge of the patient's age, gender, and underlying conditions-will help narrow the differential diagnosis.

Mixed glioneuronal tumor: A dysembryoplastic neuroepithelial tumor with rosette‐forming glioneuronal tumor component

Neuronal and mixed neuronal-glial tumors of the CNS show a wide spectrum of components. Here, we report an unusual case of brain tumor with combined histological features of dysembryoplastic neuroepithelial tumor (DNT) and rosette-forming glioneuronal tumor (RGNT) in a 23-year-old man. It arose in the left anterior cingulate cortex with a pseudo-polycystic appearance on neuroimaging. Histological features contained the "specific glioneuronal element" mimicking DNT and the components of distinct neurocytic rosettes with a center of neuropil islands and pilocytic astrocytoma resembling RGNT. Although the mechanisms of mixed glioneuronal tumor are far from being well-known, their co-existence might suggest a possible etiologic relationship between DNT and RGNT.

Olig2‐positive cells in glioneuronal tumors show both glial and neuronal characters: The implication of a common progenitor cell?

Glioneuronal tumors (GNTs) are rare neoplasms consisting of both glial and neuronal components. Among the GNTs, dysembryoplastic neuroepithelial tumors (DNTs), papillary glioneuronal tumors (PGNTs), and rosette-forming glioneuronal tumors of the fourth ventricle (RGNTs) share the character of being mainly composed of small round Olig2-positive tumor cells. Using immunohistochemistry and fluorescence in situ hybridization, we examined a series of 35 GNT cases (11 DNTs, 15 PGNTs and 9 RGNTs) on the characteristics of Olig2-positive tumor cells. Histologically, Olig2-positive cells showed small round forms in most GNTs; however, there were a small number of Olig2-positive cells with neuronal morphology only in a PGNT case. These cells expressed both glial and neuronal markers by double immunostaining. With regard to labeling indices and intensity, only PGNT cells expressed neuronal markers, including α-internexin and neurofilament. These findings also suggest that some Olig2-positive PGNT cells may show neuronal differentiation. In GNTs, a considerable number of Olig2-positive cells showed immunopositivity for cyclin D1 and/or platelet-derived growth factor receptor alpha (PDGFRα), which are markers for oligodendrocyte progenitor cells. These immunostainings were particularly strong in DNTs. In RGNTs, Olig2-positive cells formed "neurocytic rosettes". Furthermore, they were also immunopositive for glial markers, including GFAP, PDGFRα and cyclin D1. These findings indicate the heterogeneous characteristics of Olig2-positive cells in GNTs, and some of them also exhibited neuronal features. So it is possible that a part of Olig2-positive GNT cells have characteristics similar to those of progenitor cells.